CD4 and infection: The result was inconsistent with the conclusion that CD4+ T cells were the major source of IFN-γ in response to PvMSP1P-19 [38], because though most spleen IFN-γ may be produced by CD4+ T cells in the early stage of infection, at the late stage IFN-γ from CD8+ T cells could be enhanced because of compensation by other cell types [19].